iis log files - query about 404 errors

Hello,

I am looking at my log files for my site, http://jimpix.co.uk

If I look at the failure log, which states:

The Failure Report identifies requests that were made to the server that resulted in an error such as a '404 Document Not Found'

I find a number of errors. I am baffled why I get a massive bunch of static images here, e.g:

/images/hi_res/fish.jpg
/images/hi_res/tolkein.jpg
/images/hi_res/bushworld.jpg

these are not broken links, or unavailable files, since I can go to any of them:

http://jimpix.co.uk/images/hi_res/fish.jpg
http://jimpix.co.uk/images/hi_res/tolkein.jpg
http://jimpix.co.uk/images/hi_res/bushworld.jpg

and view them fine.

Why would they be flagged as 404 errors? My host doesn't know why - I checked with them first.

It makes no sense, unless the page doesn't just include 404 errors, but also 304 errors, which if I'm right is the status for cached images...

Thanks

Jim